Vertical Heterogeneity Research Articles

Untangling fuel, weather and management effects on fire severity: Insights from large-sample LiDAR remote sensing analysis of conditions preceding the 2019-20 Australian wildfires

Evaluation of fire severity reduction strategies requires the quantification of intervention outcomes and, more broadly, the extent to which fuel characteristics affect fire severity. However, investigations are currently limited by the availability of accurate data on fire severity predictors, particularly relating to fuel. Here, we used airborne LiDAR data collected before the 2019-20 Australian Black Summer fires to investigate the contribution of fuel structure to fire severity under a range of weather conditions. Fire severity was estimated using the Relative Burn Ratio calculated from Sentinel-2 optical remote sensing imagery. We modelled the effects of various fuel structure estimates and other environmental predictors using Random Forest models. In addition to variables estimated at each observation point, we investigated the influence of surrounding landscape characteristics using an innovative method to estimate fireline progression direction. Our models explained 63–76% of fire severity variance using parsimonious predictor sets. Fuel cover in the understorey and canopy, and vertical vegetation heterogeneity, were positively associated with fire severity. Up-fire burnt area and recent planned and unplanned fire reduced fire severity, whereby unplanned fire provided a longer-lasting reduction of fire severity (up to 15 years) than planned fire (up to 10 years). Although fuel structure and land management effects were important predictors, weather and canopy height effects were dominant. By mapping continuous interactions between weather and fuel-related variables, we found strong evidence of diminishing fuel effects below 20–40% relative air humidity. While our findings suggest that land management interventions can provide meaningful fire severity reduction, they also highlight the risk of warmer and drier future climates constraining these advantages.

Micropore Structure of Deep Shales from the Wufeng–Longmaxi Formations, Southern Sichuan Basin, China: Insight into the Vertical Heterogeneity and Controlling Factors

The microscopic pore throat structure of shale reservoir rocks directly affects the reservoir seepage capacity. The occurrence and flow channels of shale gas are mainly micron–nanometer pore throats. Therefore, to clarify the microstructural characteristics and influencing factors of the deep organic-rich shales, a study is conducted on the marine shale from the Upper Silurian to Lower Ordovician Wufeng–Longmaxi Formation in the southern Sichuan Basin. Petrographic lithofacies division is carried out in combination with petro-mineralogical characteristics, and a high-resolution scanning electron microscope, low-temperature nitrogen and low-temperature carbon dioxide adsorption, and micron-computed tomography are used to characterize the mineral composition and pore structure qualitatively and quantitatively, upon which the influencing factors of the microstructure are further analyzed. The results show that with the increase in burial depth, the total organic carbon content and siliceous mineral content decrease in the Wufeng formation to Long-11 subsection deep shale, while clay mineral content increases, which corresponds to the change in sedimentary environment from anoxic to oxidizing environment. Unexpectedly, the total pore volume of deep shale does not decrease with the increase in burial depth but increases first and then decreases. Using total organic carbon (TOC), siliceous mineral content showed a good correlation with total pore volume and specific surface area, with correlation coefficients greater than 0.7, confirming the predominant role of these two factors in controlling the pore structure of deep shales. This is mainly because the Longmaxi shale is already in the late diagenetic stage, and organic matter pores are generated in large quantities. Clay minerals have a negative correlation with the total pore volume of shale, and the correlation coefficient is 0.7591. It could be that clay minerals are much more flexible and are easily deformed to block the pores under compaction. In addition, the longitudinal heterogeneity of the deep shale reservoir structure in southern Sichuan is also controlled by the thermal effect of the Emei mantle plume on hydrocarbon generation of organic matter and the development of natural microfractures promoted by multistage tectonic movement. Overall, the complex microstructure in the deep shales of the Longmaxi Formation in the southern Sichuan Basin is jointly controlled by multiple effects, and the results of this research provide strong support for the benefit development of deep shale gas in southern Sichuan Basin.

Pore-Scale Characterization of CO2 Trapping and Oil Displacement in Three-Phase Flow in a Heterogeneous Layered Sandstone

Summary Permeability variation in the vertical direction, a typical sandstone reservoir heterogeneity, can trap a large amount of oil in the low-permeability layer. We performed water-alternating-gas (WAG) injection and CO2 foam flooding on a specially constructed millimeter-sized layered sandstone and investigated fluid distribution using high-resolution X-ray microtomography. Based on the segmented images, CO2 capillary-trapping capacity, oil recovery, Euler number, shaper factor, capillary pressure, and fluid flow conductivity were calculated. Our results show that increasing the number of WAG cycles favored CO2 capillary trapping, and oil recovery was enhanced by the WAG strategy. However, there was still a significant amount of oil trapped in the low-permeability layer. After the WAG injection, the connectivity of the residual oil clusters decreased, the capillary pressure of the oil clusters increased, and oil flow conductivity decreased. This was not conducive to further oil recovery. The subsequent injection of CO2 foam effectively recovered the oil in the low-permeability layer. During the no-injection period, we observed a crossflow phenomenon caused by gravity segregation (the high-permeability layer was located below the low-permeability layer), i.e., oil in the low-permeability layer decreased while oil in the high-permeability layer increased, which is beneficial for subsequent oil production. Furthermore, CO2 moved upward driven by gravity, and although capillary barriers could prevent CO2 from escaping, subsequent water injection was essential to improve the stability of CO2 capillary trapping. This work accurately quantifies the distribution of oil and gas in high- and low-permeability layers, thus providing fundamental data for oil recovery and CO2 trapping in reservoirs with vertical heterogeneity. Although the sample used in the experiment was not natural reservoir rock, our results imply that when the permeability ratio between the two layers is greater than 2, sufficient attention must be paid to the fluid distribution differences caused by this layered heterogeneity. Different displacement strategies, such as WAG and CO2 foam flooding, or gravity differences between oil and gas can be used to enhance oil recovery.

Eoarchean to Paleoproterozoic Crust History in the Yakutian Diamond Province: Evidence from U–Th–Pb (LA-ICP-MS) and Lu–Hf Dating of Zircons from Crustal Xenoliths in Kimberlite Pipes

Abstract —Radiometric dating of zircon grains from crustal xenoliths in kimberlites of the Yakutian diamond province show that most of the Daldyn and Markha terranes were formed in Paleoarchean but preserve some fragments of Eaoachean and possibly even Hadean crust recycled in several tectonothermal events. The oldest zircons were crystallized about 3.2 Ga and recrystallized during later activity stages of 2.9, 2.8–2.7, and 1.9 Ga, whereby they gained radiogenic hafnium produced by 176Lu decay in the rock. The degrees crust rework and the tectonothermal stages varied across the Anabar tectonic province. The earliest events of 3.2 and 2.9 Ga left record in zircons from kimberlites in the Nakyn field, while the signatures of the 2.7 Ga activity are best pronounced in zircons from kimberlites sampled in the Upper Muna and Nakyn fields. On the other hand, zircons from lower crustal mafic granulite xenoliths in the Daldyn and Alakit-Markha kimberlites lack traces of the earliest crust history and only evidence of the last 1.9 Ga event, which remained mute in xenolith samples from the Upper Muna field. Zircons from felsic granulite and metadiorite xenoliths in the Udachnaya kimberlite, which represent middle and upper crust, show a peak at 2.6 Ga besides that of 1.9 Ga. The synthesized available data support several previous inferences: vertical and lateral heterogeneity of the crust in the Yakutian diamond province; absence of linkage between the crust recycling degree and major collisional zones of the Siberian craton; absence of the separate Markha terrane. Correlation of age peaks corresponding to thermal events in the crust history of the Anabar tectonic province with those of large igneous provinces allows a hypothesis that the revealed tectonothermal events may be related with the activity of superplumes.

Inversion of walkaway VSP data in the presence of lateral velocity heterogeneity

Multi-azimuth walkaway vertical seismic profiling is an established technique for the estimation of in situ slowness surfaces and inferring anisotropy parameters. Normally, this technique requires the assumption of lateral homogeneity, which makes the horizontal slowness components at depths of downhole receivers equal to those measured at the surface. Any violations of this assumption, such as lateral heterogeneity or nonzero dip of intermediate interfaces, lead to distortions in reconstructed slowness surfaces and, consequently, to errors in estimated anisotropic parameters. In this work, we relax the assumption of lateral homogeneity and discuss how to correct vertical seismic profile data for weak lateral heterogeneity. We describe a procedure of downward continuation of recorded traveltimes that accounts for the presence of both vertical inhomogeneity and weak lateral heterogeneity, which produces correct slowness surfaces at depths of downhole receivers, noticing that sufficiently dense receiver coverage along a borehole is required to separate influences of vertical and lateral heterogeneity on measured traveltimes and obtain accurate estimates of the slowness surfaces. Once the slowness surfaces are found and a desired type of anisotropic model to be inverted is selected, the corresponding anisotropic parameters, providing the best fit to the estimated slownesses, can be obtained. We invert the slowness surfaces of P-waves for parameters of the simplest anisotropic model describing dipping fractures (transversely isotropic medium with a tilted symmetry axis). Five parameters of this model, namely, the P-wave velocity V0 in the direction of the symmetry axis, Thomsen's anisotropic coefficients ϵ and δ, the tilt ν, and the azimuth β of the symmetry axis, can be estimated in a stable manner when maximum source offset is greater than half of receiver depth.

Estimating soil water content in a thorny forest ecosystem by time‐lapse electrical resistivity tomography (ERT) and HYDRUS 2D/3D simulations

AbstractDetermination of soil volumetric water content in forest ecosystems is particularly challenging due to deep rooting systems and unknown soil vertical and spatial heterogeneity. This research aims to test two undisturbed methods, electrical resistivity tomography (ERT) and HYDRUS 2D/3D, for 2D determination in a thorny forest ecosystem. The experiment consisted of infiltrating 10 L of water lasting 60 min. During infiltration, ERT measured apparent resistivity by time‐lapse measurements, and was measured with an FDR probe (EnviroSCAN) at 33, 63, 83, 97, and 163 cm depth close to the infiltration site. At the end of infiltration, a soil pit was dug, and 100 measurements of were performed with a TDR in a 10 × 10 cm regular grid. Archie law transformed soil resistivity (ERT) into using manual calibration, verified by an independent dataset. The 2D profile obtained by ERT was qualitatively compared with the HYDRUS 2D/3D one. HYDRUS 2D/3D was parametrized with calibrated parameters obtained with HYDRUS 1D using 106 days of obtained with EnviroSCAN. The results of HYDRUS 1D calibration and verification were satisfactory, with RMSE and Nash‐Sutcliffe coefficients ranging from 0.021 to 0.034 cm3 cm−3 and 0.11 to 0.77, respectively. The forward HYDRUS 2D/3D simulation disagrees with EnviroSCAN data for 33 cm depth. However, it follows the trend with near to zero variation of water content at 63 cm depth. Water content determination by ERT was satisfactory with RMSE for calibration and verification of 0.017 and 0.021 cm3 cm−3. HYDRUS 2D/3D and ERT comparisons were not equal, with a shallower wetting front by ERT and a deeper one for HYDRUS. Still, both wetting fronts agree with the wetting depth estimated by EnviroSCAN. We conclude that both methods are an alternative for determination in heterogeneous and deep soils of forest ecosystems.

Experimental study on CO2 flooding characteristics in low-permeability fractured reservoirs

ABSTRACT CO2 flooding in oil reservoir is a complex process, which includes fluid flow in fractured sandstone and interaction of CO2 and displaced oil. In order to thoroughly understand the CO2 flooding characteristics in low-permeability fractured reservoirs, a series of CO2 flooding experiments were conducted based on the multi-field coupling experimental system. Considering the difference of the fractured cores, pore cores and pore-fracture model, the effect of fracture, injection pressure, CO2 phase, and heterogeneity of horizontal composite on the CO2 flooding were analyzed. The results show that the oil recovery of fractured core was 46.96%, 7.13% higher than that of pore core, and there was no relatively stable gas-oil ratio (GOR) stage. For the pore-fracture model, the final recovery of two models increased from 49.45% to 45.86% at 2 MPa to 78.83% and 77.35% at 8 MPa, and the pore core was the main contributor to enhance oil recovery. The supercritical CO2 (sc-CO2) enhanced the oil recovery in post-gas breakthrough state, which accounted for final recovery 65.02%. Compared with the vertical layered heterogeneity, the horizontal composite heterogeneity had less influence on the final oil recovery, with differences of below 2%, and the highest CO2 utilization rate was occurred at the permeability model of Low-High-Low. The work provides insight on oil recovery improvement of CO2 flooding in low-permeability fractured reservoirs.

Late Miocene landform construction in east-southern Tibet: seismic evidence and a synthetic review

The north-south striking landform perpendicular to the dominant collision zone between the Indian and Eurasian plates was constructed in east-southern Tibet (EST) during the Late Miocene. The building processes remain ambiguous, partly owing to the lack of recognition of crustal-scale architecture. Here we deployed an east-west-oriented 120 km-long short-period dense array across the northwestern corner of EST. Results from P-wave receiver functions show a mid-crustal ductile detachment atop the crystalline basement of the eastern Lhasa terrane that has displaced the overlying crust including the upper part of the Yardong-Gulu Rift (YGR) eastward for about 100 km and an offset Moho geometry left behind beneath the Nyainqentanghla Range. Combined previous studies on the vertical heterogeneity in crustal strength beneath the YGR, a synthetic view implies a decoupled crustal architecture of EST to respond the dynamic interactions between the eastward extrusion of the Tibetan Plateau and the northward penetration of the Indian plate that constitutes the Eastern Himalayan Syntaxis. The integrated processes eventually brought active landform construction in the plateau’s interior and partly contributing to the contemporaneous intensification of monsoon in SE Asia.

Impact of Formation Dip Angle and Wellbore Azimuth on Fracture Propagation for Shale Reservoir

The significant vertical heterogeneity, variations in ground stress directions, and irregular bedding interfaces make it extremely challenging to predict fracture propagation in continental shale reservoirs. In this article, we conducted a series of triaxial laboratory experiments on continental shale outcrop rocks to investigate the effects of formation dip angle and wellbore orientation on crack propagation under horizontal well conditions. Our study revealed that fracture propagation features can be categorized into four distinct types: (1) hydraulic fractures pass through the bedding interface without activating it; (2) fractures pass through and activate the bedding interface; (3) hydraulic fractures open and penetrate the bedding interface while also generating secondary fractures; and (4) hydraulic fractures open but do not penetrate the bedding interface. We found that as the dip angle decreases, the likelihood of fractures penetrating through the bedding interface increases. Conversely, as the dip angle increases, fractures are more likely to simply open the interface without penetrating it. Moreover, we observed that the well azimuth significantly affects the degree of fracture distortion. Specifically, higher azimuth angles corresponded to a higher degree of fracture distortion.

Mesozooplankton and oceanographic conditions in the North zone of Coiba National Park (Panamá, Central America)

Zooplankton plays a central role in marine trophic webs, where community indexes (diversity, abundance, and biomass) are affected by regional and local oceanographic conditions. The multinational conservation initiative, known as the Eastern Tropical Marine Corridor (CMAR) encompasses a network of Marine Protected Areas of unique and high biological diversity along the Eastern Tropical Pacific. Zooplankton studies in this area are scarce and recently conducted. In the northern zone of Coiba Island (Coiba National Park, Panamá) during the dry and rainy seasons (2019–2020), the composition, abundance, and biomass of mesozooplankton and its relationship with oceanographic variables (temperature, salinity and euphotic zone) were analyzed. In both seasons different oceanographic conditions were found with vertical heterogeneities of temperature (T) and salinity and seasonal significant differences in minimum of T and euphotic zone depth (EZ). Zooplankton abundance and total biomass showed positive associations, and maximum values during the dry season; in oblique trawls, total zooplankton biomass showed negative associations with T (−0,60) and positive with Secchi disk depth (0.67). These patterns suggest higher zooplankton productivity during dry season associated with oceanographic conditions in the North zone of Coiba Island. Organisms were classified to the lowest taxonomic level possible (Sub-family or Genus) and a total of 33 zooplankton taxa were identified. In the holoplankton the most important groups were Copepoda, Chaetognata, Appendicularia and Thaliacea, while in the meroplankton larvae of Crustacea, Echinodermatha and Mollusca were the most common groups. Zooplankton indexes (abundance, biomass and composition) were similar to those reported for other CMAR islands. Strategies recommended to strengthen biodiversity conservation in this MPA include more studies on taxonomy, trophic dynamics, and connectivity of planktonic communities as central link in marine trophic webs.

Environmental concentrations of anionic surfactants in lake surface microlayers enhance the toxicity of Microcystis blooms: Insight from photosynthesis, interspecies competition, and MC production

Anionic surfactants represented by linear alkylbenzene sulfonate (LAS) exhibit vertical heterogeneity of concentrations in aquatic environments owing to their amphiphilic structure. Field investigations showed that the concentration of anionic surfactants (mainly LAS) in the water surface microlayer (SML) of Lake Taihu reached 580 μg/L, higher than that in the lower layer. Floating Microcystis blooms overlap in space with the high concentration of anionic surfactants in SML. However, few studies have focused on the effects of anionic surfactants (e.g., LAS) on the interspecies competition between toxic and nontoxic Microcystis. In this study, coculture and monoculture experiments were conducted with both toxic and nontoxic Microcystis species to explore how the environmental concentration of LAS regulates the dominance of toxic Microcystis and toxicity from the perspective of photosynthesis, species dominance, and MC production. The results showed that LAS concentrations above 0.267 or 0.431 mg/L (depending on light conditions) selectively promoted the photosynthetic competitive advantage of toxic Microcystis, leading to its higher population proportion in the community. Additionally, LAS concentrations above 0.5 mg/L induced the synthesis and release of microcystins (MCs). The results of chlorophyll fluorescence analysis, electron microscopy and transcriptome sequencing suggested that compared with nontoxic Microcystis, toxic Microcystis can better resist LAS stress by dissipating excess light, maintaining an intact membrane structure and maintaining cellular homeostasis. Transcriptome sequencing revealed that the photosynthetic damage of nontoxic Microcystis might be attributed to the impacts of LAS on the absorption and assimilation of nitrogen, which finally resulted in the degradation of phycobilisomes. This study can provide novel insight for establishing standards and safety management of wastewater discharge.

Climate and soil properties regulate the vertical heterogeneity of minor and trace elements in the alpine topsoil of the Hengduan Mountains

Soil minor and trace elements are vital regulators of ecological processes that sustain alpine ecosystem functions. In this study, the vertical pattern and driving factors of element concentrations in alpine soils of the Tibetan Plateau were investigated. Three snow mountains (Meili, Baima, and Haba) part of the Hengduan Mountain range, were selected as the study area to determine the vertical distribution of 12 typical elements (Cr, Ni, Cu, Fe, Mn, Zn, Cd, Pb, Ca, Sr, As, and Se) in topsoil with increasing and decreasing elevation, as well as the dominant driving factors of their spatial heterogeneity. Results showed that all elements, except Se, showed strong vertical heterogeneity, among which Cr, Ni, Cu, and Fe showed peak concentrations at 2700–3000 m; the highest concentrations of Mn and Zn were at 3200 m and 2700 m, with Cd and Pb at 2500 m. Ca and Sr levels gradually decreased with increasing elevation. According to the structural equation model and random forest analysis, the vertical heterogeneity of soil elements is directly regulated by the variability of climate and soil properties due to changes in elevation. A three-way PERMANOVA further quantized the contributions of climate and soil properties on vertical heterogeneity of all soil elements, which were 35.2 % and 50.5 %, respectively. This study used various statistical tools to reveal the dominant factors affecting the vertical heterogeneity of soil elements. These findings provided a scientific overview of element distribution on the Tibetan Plateau and significant references for the vertical distribution of elements in the topsoil of other snow mountains worldwide.

Assessment of the interactions between soil–biosphere–atmosphere (ISBA) land surface model soil hydrology, using four closed-form soil water relationships and several lysimeters

Abstract. Soil water drainage is the main source of groundwater recharge and river flow. It is therefore a key process for water resource management. In this study, we evaluate the soil hydrology and the soil water drainage, simulated by the interactions between soil–biosphere–atmosphere (ISBA) land surface model currently used for hydrological applications from the watershed scale to the global scale, where parameters are generally not calibrated. This evaluation is done using seven lysimeters from two long-term model approach sites measuring hourly water dynamics between 2009 and 2019 in northeastern France. These 2 m depth lysimeters are filled with different soil types and are either maintained as bare soil or covered with vegetation. Four closed-form equations describing soil water retention and hydraulic conductivity functions are tested, namely the commonly used equations from Brooks and Corey (1966) and van Genuchten (1980), a combination of the van Genuchten (1980) soil water retention function with the Brooks and Corey (1966) unsaturated hydraulic conductivity function, and, for the very first time in a land surface model (LSM), a modified version of the van Genuchten (1980) equations, with a new hydraulic conductivity curve proposed by Iden et al. (2015). The results indicate good performance by ISBA with the different closure equations in terms of soil volumetric water content and water mass. The drained flow at the bottom of the lysimeter is well simulated, using Brooks and Corey (1966), while some weaknesses appear with van Genuchten (1980) due to the abrupt shape near the saturation of its hydraulic conductivity function. The mixed form or the new van Genuchten (1980) hydraulic conductivity function from Iden et al. (2015) allows the solving of this problem and even improves the simulation of the drainage dynamic, especially for intense drainage events. The study also highlights the importance of the vertical heterogeneity of the soil hydrodynamic parameters to correctly simulate the drainage dynamic, in addition to the primary influence of the parameters characterizing the shape of the soil water retention function.

Analysis Reveals Depth of Vaca Muerta’s Potential

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 205573, “Vaca Muerta: An Emerging Shale Petroleum Reservoir,” by Rahimah B. A. Karim and Roberto Aguilera, SPE, University of Calgary. The paper has not been peer reviewed. _ The objective of the complete paper is to present geological and reservoir characterization, drilling and production strategies, historical performance, and economics of the Vaca Muerta reservoir. The word “petroleum” as used in this paper includes oil, natural gas, and natural-gas liquids. The authors conclude that oil and gas potential in the Vaca Muerta shale is significant and rivals the potential of shales widely developed in the United States and Canada. Reservoir Background In 2008, exploration activities began in the Loma Campana (LC) field, leading to Vaca Muerta’s discovery in 2010. The LC area was selected as the first factory-mode development because of its pre-existing infrastructure and accessibility. The urgency of boosting hydrocarbon production in Argentina has driven multiple companies to invest substantially in unconventional resources. The complete paper details the shale’s geological setting and reservoir characterization. Reservoir heterogeneity and its effect on productivity are described for selected development areas, including La Amarga Chica (LAC), the central area, and LC. Vaca Muerta is an attractive target for shale development because of a few factors. One is its thermal maturity that increases from east to west. This has resulted in multiple types of hydrocarbon windows, from oil to dry-gas windows. Furthermore, it is laterally extensive and has formation thickness of up to 500 m. Total organic carbon (TOC) also is high (2–10%), with a mineralogy content of less than 30% clay. At the basin level, the average matrix porosity of Vaca Muerta ranges from 4 to 14%, with a narrower range at the field or block scale. The formation shows similarities with other well-known shale plays with similar porosity volumes and pore types, such as the Haynesville (between 8 and 16%) but higher than the Eagle Ford (between 8 and 10%). Significant formation thickness drove the application of vertical wells during the first factory drilling in Vaca Muerta. It allowed placement of four to six hydraulic fractures controlled by the lithologies and vertical heterogeneity. In 2015, however, a major change from vertical to horizontal well development occurred as a result of better understanding of the formation complexity and optimal landing zones. In the past few years, operators have increased lateral length from 1000 to 2500 m to improve productivity. Most operations use multiwell pad drilling. The pad is a four-well line with 10-m spacing on the surface and a minimum of 300-m spacing in the reservoir. This well spacing is wide by US standards but is optimal for Vaca Muerta to minimize well interference in the reservoir.

The capillary pressure curves from upscaling interfacial and unsaturated flows in porous layers with vertical heterogeneity

We provide the capillary pressure curves pc(s¯) as a function of the effective saturation s¯ based on the theoretical framework of upscaling unsaturated flows in vertically heterogeneous porous layers proposed recently (Z. Zheng, Journal of Fluid Mechanics, 950, A17, 2022). Based on the assumption of vertical gravitational-capillary equilibrium, the saturation distribution and profile shape of the invading fluid can be obtained by solving a nonlinear integral-differential equation. The capillary pressure curves pc(s¯) can then be constructed by systematically varying the injection rate. Together with the relative permeability curves k¯rn(s¯) that are already obtained. One can now provide quick estimates on the overall behaviours of interfacial and unsaturated flows in vertically-heterogeneous porous layers.

α-Diversity of plant communities, forest birds and wood-decaying fungi in urban parks of a metropolis

The biodiversity of urban parks is an indicator object of monitoring biodiversity under conditions of constant recreational pressure. The main approaches to these issues are based on measuring the indices of vertical and horizontal heterogeneity of parklands, which make it possible to identify links between plant, wood-decaying fungi and bird diversities. As in the case of Kyiv, Ukraine, we augmented existing published data with new compositions, links and α-diversity indices of plant, fungi and bird communities in the parks of a metropolis! The infraction of α-diversity (diversity, dominance, and evenness indices) and the compositions in the communities depending on the level of recreational transformation of the parks were established. The main driving factors of α-diversity in urban parks were shown. Further research is needed to use these relationships to indicate the state of park ecosystems.Keywords: plant, vegetation; forest birds; wood-decaying fungi; recreational impact; diversity index, dominance index, evenness index

Seismic velocity structure of the crust and uppermost mantle beneath the Tien Shan and its adjacent areas

The Tien Shan and its adjacent areas have been a prime place to understand the process of continental collision, the mechanism of mountain building and the interaction of tectonic blocks. In this study, we collect seismic data recorded by 74 broad-band stations from the China Provincial Digital Seismic Networks and the Regional Kyrgyzstan and Kazakhstan Networks between January, 2007 and September, 2009. A joint inversion technique that combines three types of datasets (receiver functions, phase velocities of Rayleigh wave measured from both ambient noise and teleseismic earthquake data) is applied to image the crustal and upper mantle structure beneath the Tien Shan and its adjacent areas. The average crustal thickness in the study area is about 50 km, however, the Moho depth extends to ∼70 km beneath the Kyrgyz Platform near the southwestern Tien Shan. Our velocity models show a good correlation with subsurface geological features at shallow depths: low velocities are predominantly observed beneath the basins due to thick sedimentary layer, whereas high velocities are mainly distributed beneath the mountain ranges due to crystalline basement rocks. In the upper mantle a low velocity zone is obviously observed beneath the western Tien Shan. Both the crust thickness and S wave velocity structure of the Tien Shan and its adjacent regions display obvious horizontal and vertical heterogeneities from west to east, which suggests that the far-field effects of the collision between Eurasian plate and Indian plate plays an important role in the tectonic activity of the Tien Shan. The apparent velocity heterogeneities beneath the northern Tarim Basin may indicate that the Tarim Basin may have been eroded and damaged by upwelling hot materials from the upper mantle.

Hydraulic conductivity estimation and lithological classification of an esker aquifer system using surface electrical resistivity surveys and a neural network

Empirical and theoretical relationships between hydraulic conductivity, lithology, and electrical resistivity provide a basis for the use of electrical resistivity for aquifer characterization in unconsolidated sediments. This study demonstrates a meaningful field-scale correlation between vertically distributed hydraulic conductivity obtained from packer-based borehole hydraulic tests, and electrical resistivity obtained from surface-based geophysical surveys over the Vars-Winchester esker aquifer system, Ontario, Canada. Electrical resistivity alone has order-of-magnitude predictive capacity for hydraulic conductivity, but is insufficient to reliably discriminate between aquifer and aquitard lithology. An alternative methodology is developed that takes advantage of the observed correlation between hydraulic conductivity and elevation, and the separability of lithology in terms of elevation. Electrical resistivity and elevation are combined as predictor variables for hydraulic conductivity using both multiple linear regression and nonlinear neural network regression, and for neural network classification of lithology. Neural network regression results in prediction accuracy for log-transformed hydraulic conductivity of 0.38–0.52 with clear definition of vertical and lateral heterogeneity. Classification accuracy for lithology is 83–84% with high probability of discrimination between the unconsolidated aquifer and aquitard sediments, and lower probability identification of the bedrock surface due to fewer samples at depth and limited penetration depth of the resistivity survey.

Evaluation of the nature of saturation of the reservoirs of the achimov formation by well-logging in conditions of low permeability and facies heterogeneity

Despite the fact that the history of studying the geology of the achimov formation spans several decades, the volume of depletion of the reserves of these deposits is small, and the number of fields where the achimov formations have been put into commercial development is few. This is due to the complex geological structure of the reservoirs, vertical and lateral heterogeneity, reduced porosity and permeability properties, and low values of the oil saturation factor. In the presented work, a generalization and analysis of all petrophysical information was made, typification of sections according to well logging with the possibility of using individual petrophysical function to assess the nature of reservoir saturation and the hydrocarbon saturation index. To create a petrophysical substantiation of well logging interpretation, both historical and current core studies in the framework of this study by the authors of the article were involved. The typification of the sections of the achimov formation was carried out on the basis of a detailed lithological study of the core using special studies such as scanning electron microscopy and computed microtomography. Identification of different types of section will allow in the future to correct the further hydrodynamic model for predicting the nature of the inflow and will significantly increase the reliability of assessing the nature of saturation and the hydrocarbon saturation index of heterogeneous deposits of the achimov formation.

Fast Secondary Aerosol Formation in Residual Layer and Its Impact on Air Pollution Over Eastern China

AbstractThough China's air quality has been improved in the past decade, haze still engulfs megacities in winter with fast increasing secondary aerosol like nitrate. Given that aerosol and its precursors exhibit great vertical heterogeneity, we conducted airship measurements at Shanghai in December 2017 to understand the critical drivers for the rapidly increased secondary pollution. By integrating in‐situ observations and model simulations, we found that cold front favors the long‐range transport of pollutants, during which chemical formation of nitrate in residual layer was faster than near the surface due to concentrated precursors and sufficient oxidation. The nitrate aloft would be entrained down once the daytime convective boundary layer develops, thereby deteriorating near‐surface air pollution. It is shown that the local surface‐level chemical production played a minor role, whereas the synoptic weather and boundary layer evolution largely contributed to enhanced secondary aerosol pollution (>60%). This study demonstrates that weather systems, boundary layer evolution, and chemical processes could jointly shape secondary aerosol production, highlighting the importance of a vertical understanding of haze pollution.